Basic Functions; Monitoring Functions - Siemens S5-155U System Manual

Power Supply Units

Basic functions

Monitoring functions

4 - 22
The power supply units offer the following functions:
• • System power supply
All the system voltages required for operation of the modules in a
CC or EU are supplied.
• • Power supply for backup (in the CC and EU 185)
A lithium battery and a rechargeable battery ensure data backup
when the system voltage is switched off or fails.
- The lithium battery remains in the CC/EU and ensures backup,
even during replacement of the power supply unit
-
During replacement or failure of the lithium battery, the
rechargeable battery in the power supply continues to provide
backup and ensures that no data are lost.
- Situated on the front plate of the power supply unit are two
sockets for input of an external battery voltage.
• • Heat removal
Three independent fans which are individually replaceable during
operation remove the dissipated power. If a fan fails, the supply
voltage for this fan is switched off and the other two fans continue
operation at increased speed.
The power supply units contain monitoring functions to detect the
following faults:
• •
Failure of system voltage
• •
Failure of output voltages
• •
Failure of an externally applied 24 V DC load voltage
(voltage monitor)
• •
Fan failure or inadequate air flow
• •
Battery failure
• •
Rechargeable battery failure
In this context, a voltage failure is equivalent to a drop of the
monitored voltage below a preset limit (see Section 4.3.6 of the
Technical Specifications).
System Manual
C79000-B8576-C199-03